feat: add date range filtering

[mloncarevich]

Summary

• Add --since / -s flag to filter commits after a date
• Add --until / -u flag to filter commits before a date
• Recalculates all stats (authors, streaks, activity) for filtered range
• Includes date filter info in JSON output

Usage

# Stats for 2025 only
gitstats stats --since 2025-01-01 --until 2025-12-31

# Stats from last month
gitstats stats --since 2026-01-01

# Combine with JSON
gitstats stats --since 2025-06-01 --json

Example output

📊 Git Statistics for: .
Filtered: from 2025-01-01 to 2025-12-31

Total commits: 127
...

Made with Cursor